CHROMIUM: drm/exynos: gem: Combine duplicate error handling in gem_create

CHROMIUM: drm/exynos: gem: Combine duplicate error handling in gem_create

The error handling for buffer creation is the same for both CONTIG and
NONCONTIG, so refactor a bit.

Signed-off-by: Daniel Kurtz <djkurtz@chromium.org>
BUG=chromium-os:37097
TEST=builds clean; sanity check boot on device

Change-Id: I296198291f06fe3dda9b9989ea139badbba53004
Reviewed-on: https://gerrit.chromium.org/gerrit/40442
Reviewed-by: Stéphane Marchesin <marcheu@chromium.org>
Commit-Queue: Daniel Kurtz <djkurtz@chromium.org>
Reviewed-by: Daniel Kurtz <djkurtz@chromium.org>
Tested-by: Daniel Kurtz <djkurtz@chromium.org>